Power divider for motor vehicles comprising an off-road speed gear and a set-off-out-put

ABSTRACT

A power-split transmission for motor vehicles with off-road travel consists of a case ( 1 ), of an input shaft ( 2 ), of a first output shaft ( 3 ) coaxial with the latter, of a second output shaft ( 4 ), of a reduction unit ( 5 ), of a clutch unit ( 6 ) and of an offset drive ( 7 ). In order to make the power-split transmission compact, with low loss and low noise and synchronizable, the reduction unit ( 5 ) consists of: a central driving gearwheel ( 11 ) on a first hollow shaft ( 12 ), a central ring gear ( 13 ) with a second hollow shaft ( 14 ), first and second intermediate gearwheels ( 15, 16 ) with an axle fixed to the case, in each case the first intermediate gearwheel ( 15 ) meshing with the central driving gearwheel ( 11 ), the second intermediate gearwheel ( 16 ) with the central ring gear ( 13 ) and the first and second intermediate gearwheels ( 15, 16 ) with one another, and a power take-off shaft ( 17 ), and the clutch unit ( 6 ) consists of: primary parts ( 21, 24 ) on the input shaft ( 2 ) and on the second hollow shaft ( 14 ), secondary parts ( 22, 23 ) on the power take-off shaft ( 17 ) and on the first hollow shaft ( 12 ), a first shift sleeve ( 25 ) and a second shift sleeve ( 26 ) for changing over between road travel and off-road travel.

BACKGROUND OF THE INVENTION

[0001] The invention is concerned with a power-split transmission formotor vehicles with off-road travel, consisting of a case, of an inputshaft, of a first output shaft coaxial with the latter, of a secondoutput shaft offset with respect to said first output shaft, of areduction unit, of a clutch unit and of an offset drive. This form ofpower-split transmission is also designated as “single-offset”. It isused, above all, for all-wheel driven passenger motor vehicles and lightcommercial vehicles with a longitudinally arranged engine/transmissionblock, while there can be a changeover from road travel to off-roadtravel by means of the reduction unit, an interaxle differential isoften dispensed with and the drive of the second driven axle can be cutin.

[0002] A generic power-split transmission is known from EP 943 479 A1.In this, the reduction unit on the side of the input shaft is aplanetary transmission with a ring gear fixed to the case and with powertake-off at the planet carrier. Directly behind, the associated shiftdevice is accommodated. This is followed, in one embodiment (FIG. 2), bya central differential and then the driving wheel of the offset drive;in another embodiment (FIG. 9), it is the driving wheel of the offsetdrive and, finally, a clutch for cutting in the second driven axle.

[0003] The reduction unit has various disadvantages. On account of thering gear fixed to the case, the planetary transmission corotates withmeshing even in road travel, thus increasing the losses, wear andgeneration of noise. Moreover, in the case of single-stage planetarytransmissions of this form of construction, the design for achieving thereductions (2:1 to 3:1) customary for off-road travel results inunfavorably small planet wheels. The shift device between the planetarytransmission and the driving wheel of the offset drive is not readilyaccessible, increases the construction length and displaces the offsetdrive to the rear, the latter factor being unfavorable, inter alia, forreasons of the radiation of solid-born sound through the case.

[0004] The object of the invention is, therefore, to eliminate theforegoing disadvantages. The power-split transmission is to be short andcompact, with low loss and low noise and also suitable formodularization and the mounting of synchronization.

SUMMARY OF THE INVENTION

[0005] The foregoing object is achieved, according to the invention,wherein the reduction unit forms a fixed-shaft transmission, but couldalso be designated as a planetary transmission with a planet carrierfixed to the case and with a Ravigneaux-type gear set. The twointermediate gearwheels prevent a reversal in direction of rotationbetween the drive and the power take-off and afford wide freedom ofconfiguration in the implementation of reduction. Reductions of between2:1 and 3:1 can be implemented optimally. A further advantage of theplanet carrier fixed to the case is that the central driving gearwheeland the central ring gear are centered by the intermediate wheels, sothat they do not need specific radial bearings. Axial bearings, whichare necessary in any case with helical toothing, are sufficient.

[0006] Together with the hollow shafts and the clutch unit according tothe invention, a particular advantage is also achieved: in road travel,the reduction unit is not only taken out of the force flux, but may evenbe stationary. The drive-through from the input shaft via the clutch tothe power takeoff shaft is direct. Road travel is therefore virtuallyloss-free and noiseless.

[0007] By means of the two hollow shafts, the clutch unit can be drawnout of the reduction unit and arranged in front or behind of the latter,thus reducing the overall length of the case and, as will be shownlater, assisting the addition of synchronization.

[0008] The clutch unit consists of two primary parts and two secondaryparts which, in the simplest instance, may be sliding-sleeve clutcheswhich can be connected to one another in various ways by means of thetwo shift sleeves. The first shift sleeve serves for the rotationallyfixed connection of the input shaft to the first hollow shaft inoff-road travel, and the second shift sleeve serves for the rotationallyfixed connection of the input shaft to the power take-off shaft in roadtravel and for connecting the second hollow shaft to the power take-offshaft in off-road travel.

[0009] The two hollow shafts are preferably led out of the reductionunit forward on the side facing the input shaft. In this case, thesecond hollow shaft is arranged within the first hollow shaft. Theclutch unit can thereby be arranged outside the reduction unit where itis easily accessible and is not restricted in diameter.

[0010] In a particularly simple embodiment without a centraldifferential, the power take-off shaft can be connected fixedly in termsof rotation to a driving wheel of the offset drive via a cut-in clutch.The case can therefore be made particularly short, insofar as the samecase is not also used for a version with a central differential in amodular form of construction.

[0011] In the preferred embodiment with a central differential, thepower take-off shaft is drive-connected to a central differential whichis designed as a planetary transmission and two axle drive shafts ofwhich can be connected fixedly in terms of rotation selectively to adriving wheel of the offset drive in each case via a cut-in clutch. Thecentral differential designed as a planetary transmission increases theoverall length only slightly. The cut-in clutch may be arranged behindthe planetary transmission, so that the second output shaft is alsorelatively far forward. Overall, an extremely compact form ofconstruction is achieved in this way, because the two clutches are drawnout of the transmission forward and rearward.

[0012] The preferred design of the central differential according to thepresent invention provides a Ravigneaux-type gear set which affords theadvantages, apart from the short overall length, that the ratio of thetorques metered to the first and to the second output shaft can beadapted to the vehicle-specific requirements simply by the choice of thenumber of teeth of the sun wheel, and that no reversal in direction ofrotation takes place. Since this advantage also applies to the reductionstage, what can easily be achieved is that the ring gear and thedifferential ring gear and/or the intermediate gearwheels and the planetwheels are identical parts. The cost saving achieved by means of thismeasure is obvious.

[0013] In a development of the invention, the cut-in clutch hascomprising first, second and third couplings. The coupling parts are, inthe simplest instance, hubs with coupling teeth and are arranged behindthe central differential. As a result, there is wide freedom in theirconfiguration which also allows the addition of synchronization. Thus,even with a single clutch sleeve, two-wheel drive, four-wheel drive withlongitudinal balancing via the central differential and four-wheel drivewith differential lock may be selected and may be shifted in theappropriate sequence.

[0014] If all the advantages are utilized, the subassemblies of thepower-split transmission may be arranged in such a way that thereduction unit and the central differential are directly adjacent, beingfollowed, in the direction of the first output shaft, first by theoffset drive and then by the cut-in clutch. The installation dimensionsare thus minimized, the case becomes short and rigid and the offsetdrive can be arranged very far forward.

[0015] Also, by all the advantages being utilized, so much constructionspace is available for the clutch unit and for the cut-in clutch thatthe clutches can be provided with synchronizations which must meet veryhigh requirements during the pronounced stage jump between road traveland off-road travel or in the case of the high rotational speeddifference when one of the axles loses wheel adhesion. Theserequirements can be satisfied by large diameters of the synchronizedclutch parts.

[0016] In a particularly refined design of the clutch unit, the secondshift sleeve itself is connected fixedly in terms of rotation, butaxially displaceably, to the power take-off shaft, and the first shiftsleeve and the second shift sleeve are jointly displaceable in the axialdirection, but with axial play, so that, during the shift back into theoff-road travel, first the first shift sleeve is synchronized with thefirst hollow shaft and then the second shift sleeve is synchronized withthe second hollow shaft. Synchronization thus takes place in two stages,first for the lower torque for the acceleration of a central wheel andintermediate wheels and only then for the torque at the ring gear whichis higher as a consequence of reduction. Thus, even in extreme drivingsituations, a reliable shift back into off-road travel during driving isensured.

[0017] In the case of a synchronizing cut-in clutch, the third shiftsleeve has first coupling parts which are connected fixedly in terms ofrotation, but axially displaceably, to the second axle drive shaft. If,further, the third shift sleeve is displaceable in the axial directionwith respect to the first coupling parts, the third shift sleeve can,unimpeded by the first coupling parts, lock the differential.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention is described and explained below by means ofillustrations of some embodiments of the subject of the invention inwhich:

[0019]FIG. 1 illustrates a diagrammatic longitudinal section through afirst simple embodiment,

[0020]FIG. 2 illustrates a cross section according to 2-2 in FIG. 1,

[0021]FIG. 3 illustrates a diagrammatic longitudinal section through asecond embodiment,

[0022]FIG. 4 illustrates a cross section according to 4-4 in FIG. 3,

[0023]FIG. 5 illustrates a diagrammatic longitudinal section through avariant of the second embodiment with synchronization,

[0024]FIG. 6 illustrates, enlarged, the detail 6 in FIG. 5,

[0025]FIG. 7 illustrates, enlarged, the detail in FIG. 5.

DETAILED DESCRIPTION

[0026] In FIG. 1, the case of a power-split transmission is merelyindicated and designated by 1. The power-split transmission is connectedvia an input shaft 2 to a motor/transmission unit, not illustrated, viaa first output shaft 3, coaxial with the input shaft 2, to an axle,preferably the rear axle of an all-wheel driven motor vehicle, and via asecond output shaft 4 to a second driven axle, preferably the frontaxle. The case 1 accommodates, as subassemblies of the power-splittransmission, a reduction unit 5, a clutch unit 6 and an offset drive 7for driving a second output shaft 4 offset with respect to the firstoutput shaft 3.

[0027]FIG. 2 shows the engagement conditions in the reduction unit 5.The reduction unit 5 consists of a central driving gearwheel 11 on afirst hollow shaft 12 (FIG. 1), of a central ring gear 13 on a secondhollow shaft 14 and of at least two pairs of gearwheels 15, 16. 15 is ineach case a first intermediate gearwheel and 16 a second intermediategearwheel, in each case the first 15 meshing with the central drivinggearwheel 11, the second 16 with the central ring gear 13 and both 15,16 with one another. The first and second intermediate gearwheels 15, 16rotate about spatially fixed axles which are part of anintermediate-gearwheel carrier 18 fixed to the case or are fixedlyconnected to said carrier.

[0028] As a consequence of the arrangement, the first hollow shaft 12surrounds the second hollow shaft 14. Within the second hollow shaft 14is provided a power take-off shaft 17. The two hollow shafts 12, 14constitute the connection between the reduction unit 5 and the clutchunit 6, the power take-off shaft 17 passing through the reduction unit5.

[0029] The clutch unit 6 consists of a first primary part 21 connectedfixedly in terms of rotation to the input shaft 2, of the firstsecondary part 22 connected fixedly in terms of rotation to the powertake-off shaft 17, of a second secondary part 23 connected fixedly interms of rotation to the first hollow shaft 12 and of a second primarypart 24 connected rotatably to the second hollow shaft 14. In theexemplary embodiment shown, these parts are designed in each case asclutch hubs. For changing over between road travel and off-road travel,they are connected, in each case in different ways, by means of a firstshift sleeve 25 and a second shift sleeve 26.

[0030] The clutch unit 6 is illustrated in two different positions: inthe “road travel” position below the axis of the power take-off shaft 17and in the “off-road travel” position above it. In road travel, thesecond shift sleeve 26 (position 26′) connects the first primary part 21to the first secondary part 22 and therefore the input shaft 2 to thepower take-off shaft 17. The shift sleeve 25 does not perform anyfunction in this position, and the two hollow shafts 12, 14 aretherefore free and may be stationary during driving in road travel. Thismeans that the entire reduction unit 5 is stationary.

[0031] In off-road travel, the first shift sleeve 25 connects the firstprimary part 21 to the second secondary part 23 and therefore the inputshaft 2 to the first hollow shaft 12 which constitutes the input of thereduction unit 5. The second shift sleeve 26 connects the second primarypart 24 to the first secondary part 22 and therefore the second hollowshaft 14 to the power take-off shaft 17. The power take-off shaft 17 isdrive-connected to the driving wheel 28 of the offset drive 7 via acut-in clutch 27. The offset drive itself consists, here, of the drivingwheel 28, of an intermediate wheel 29 and of a driven wheel 30, butcould just as well be a traction drive.

[0032]FIG. 3 shows a power-split transmission in a form of constructionin which it is extended by a central differential 8. Since it differsmerely in the central differential and in a changed cut-in clutch, onlythese subassemblies are described here. The power take-off shaft 17 doesnot lead directly to the first output shaft 3 here, but to a centraldifferential 8. Said power take-off shaft is connected fixedly in termsof rotation to the differential ring gear 34 of the central differential8. Overall, the central differential 8 consists of the differential ringgear 34 connected fixedly in terms of rotation to the power take-offshaft 17, of a sun wheel 35 connected fixedly in terms of rotation to asecond axle drive shaft 32 and of a planet carrier 36 connected fixedlyin terms of rotation to the first axle drive shaft 31 and having firstand second planet wheels 37, 38, in each case the first planet wheel 37meshing with the sun wheel 35, the second planet wheel 38 with thedifferential ring gear 34 and the first and second planet wheels 37, 38with one another.

[0033]FIG. 4 shows the engagement conditions in the central differential8. The ring gear 13 of the reduction stage 5 and the differential ringgear 34 and/or the intermediate gearwheels 15, 16 and the planet wheels37, 38 may be identical parts.

[0034] Further to FIG. 3: the output of the central differential 8 isformed by a first axle drive shaft 31 for driving the rear axle and by asecond axle drive shaft 32. The driving wheel 28 of the offset drive 7is seated, here, on a third hollow shaft 45. In the arrangement shown,first, the second axle drive shaft 32 designed as a hollow shaft islocated inside this third hollow shaft 45 and the first axle drive shaft31 is located within said second axle drive shaft. These three shaftscan be connected in various ways again by means of a cut-in clutch 33.

[0035] The cut-in clutch 33 consists of first coupling parts 41connected fixedly in terms of rotation to the first axle drive shaft 31,of second coupling parts 42 connected fixedly in terms of rotation tothe second axle drive shaft 32, of third coupling parts 43 connectedrotatably to the third hollow shaft 45 and of a third displaceableclutch sleeve 44. In the version illustrated, the coupling parts 41, 42,43 are coupling hubs with coupling toothing.

[0036] The third clutch sleeve 44 can assume three positions: in theposition 44 (upper half of the figure) for all-wheel drive withdifferential action, it connects the second coupling parts 42 to thethird coupling parts 43 and therefore the sun wheel 35 to the thirdhollow shaft 45 and to the driving wheel 28, mounted thereof, of theoffset drive 7. In the second position 44′(lower half of the figure) forall-wheel drive with locked differential, it connects the first couplingparts 41 to the second and third coupling parts 42, 43 and therefore thefirst axle drive shaft 31 to the third hollow shaft 45 and, moreover,two members (sun wheel 35 and planet carrier 36) of the centraldifferential 8 to one another. In the third position 44″(drawn out, in athin line), it connects the first coupling parts 41 to the secondcoupling parts 42 only, so that the third hollow shaft 45 is freelyrotatable and the central differential 8 is locked.

[0037] The embodiment of FIG. 5 differs from that of FIG. 3 only in thatthe clutch unit 50 for the reduction unit and the cut-in clutch 33 forthe central differential are synchronized. The two clutches are shown,enlarged, in FIGS. 6 and 7. They may be flanged to the case 1 of thepower-split transmission in separate case parts.

[0038] The synchronized clutch unit 50 shown in FIG. 6 consists of afirst primary part 51 connected fixedly in terms of rotation to theinput shaft 2, of a first secondary part 52 connected to the input shaft2 fixedly in terms of rotation, but axially displaceably (splined shaftconnection 58), of a second secondary part 53 connected fixedly in termsof rotation to the first hollow shaft 12 of the reduction unit 5, of asecond primary part 54 connected fixedly in terms of rotation to thesecond hollow shaft 14, and of a first shift sleeve 55 and of a secondshift sleeve 56. The first primary part 51 is again designed as a hubwith a synchronizable contact surface and with one half of a slidingclutch 59. The contact surface may be a coupling toothing withassociated synchronization, which is not dealt with in any more detailhere because a multiplicity of suitable synchronizations are known. Thefirst secondary part 52 possesses, here, two contact surfaces 52′, 52″,and its hub is axially displaceable on the power take-off shaft 17 bymeans of a splined shaft connection 58 and, moreover, is in one piecewith the second shift sleeve 56. The second secondary part 53 and thesecond primary part 54 are also again designed to be synchronizable.

[0039] By the second shift sleeve 56 and consequently the firstsecondary part 52 being displaced, either the first contact surface 52′can be brought into engagement with the first primary part 51 or thesecond contact surface 52″ can be brought into engagement with thesecond primary part 54. The first shift sleeve 55 carries the otherclutch half of the sliding clutch 59, via which it is always connectedfixedly in terms of rotation to the second input shaft 2. Said firstshift sleeve possesses, at its other end, a further coupling surface 55′which can be brought synchronizably into engagement with the secondsecondary part 53. Further, the second shift sleeve 56 is guided freelyrotatably and with axial play 57 in said first shift sleeve.

[0040] The upper half of the figure shows the position in road travel.The transmission of force takes place from the input shaft 2 via thefirst primary part 51 to the first contact surface 52′ of the firstsecondary part 52 and from there to the power take-off shaft 17. Fortransition into off-road travel, the first shift sleeve 55 is displacedto the right, and, because of the sliding clutch 59, it always remainsdrive-connected to the input shaft 2. During displacement, first, thefurther contact surface 55′ of the first shift sleeve 55 comes intocontact with the second secondary part 53 and thus synchronizes thecentral output gearwheel 11 of the reduction unit 5 via the first hollowshaft 12. In the case of further displacement, during which the axialplay 57 between the two shift sleeves 55, 56 is used up, the secondcontact surface 52′ is also connected to the second primary part 54 andsynchronizes the remaining parts. Synchronization is thereby subdividedinto two phases.

[0041] The cut-in clutch 33 is constructed in a similar way in FIG. 7.It consists of first coupling parts 61 connected fixedly in terms ofrotation to the first axle drive shaft, of second coupling parts 62connected to the second axle drive shaft 32 fixedly in terms ofrotation, but displaceably by means of a splined shaft connection 67, ofthird coupling parts 63 connected fixedly in terms of rotation to thethird hollow shaft 45 and of a third clutch sleeve 64. The firstcoupling parts 61 are again arranged on a hub and additionally carryfirst coupling teeth 65. Their contact surface can be synchronized inwhatever way. The second coupling parts 62 are connected fixedly interms of rotation to the third clutch sleeve 64 via a sliding connection68. The second coupling parts 62 can be brought into engagementselectively either by their first coupling surface 62′ with the thirdcoupling parts 63 or by their second coupling surface 62″ with the firstcoupling parts 61.

[0042] Further, the third clutch sleeve 64 possesses two coupling teeth66 for cooperation with the first coupling teeth 65 on the firstcoupling parts 61.

[0043] There are three positions: the first position (upper half of thefigure) is all-wheel drive with differential action. The second axledrive shaft 32 is connected to the third hollow shaft 45. The secondposition (lower half of the figure) corresponds to the drive of only therear axle via the first axle drive shaft 31. By means of therotationally fixed connection of the two axle drive shafts 31, 32 viathe first coupling parts 61 and the second coupling parts 62, thedifferential is thus locked. A neutral position is possible betweenthese two positions. The third position is indicated by a thin lineabove the first half of the figure.

[0044] During the further displacement of the third clutch sleeve 64 outof the position for all-wheel drive in the upper half of the figure tothe left, although the second coupling part 62 cannot move any furtherto the left, nevertheless, as a result of the rotationally fixed slidingconnection 68, the third clutch sleeve 64 can be further displaced untilthe first and second coupling teeth 65, 66 are in engagement. Since thetwo axle drive shafts 31, 32 are thereby connected fixedly to oneanother, the differential is locked. The third clutch sleeve 64possesses an annular groove 69, at which a shift fork, not illustrated,can act for shifting purposes.

1. A power-split transmission for motor vehicles with off-road travel,consisting of a case, of an input shaft, of a first output shaft coaxialwith the latter, of a second output shaft offset with respect to saidfirst output shaft, of a reduction unit, of a clutch unit and of anoffset drive, wherein the reduction unit (5) consists of: a) a centraldriving gearwheel (11) which is connected fixedly in terms of rotationto a first hollow shaft (12), b) a likewise central ring gear (13) whichis connected fixedly in terms of rotation to a second hollow shaft (14),c) first and second intermediate gearwheels (15, 16) with an axle fixedto the case, in each case the first intermediate gearwheel (15) meshingwith the central driving gearwheel (11), the second intermediategearwheel (16) with the central ring gear (13) and the first and secondintermediate gearwheels (15, 16) with one another, d) a power take-offshaft (17), and wherein the clutch unit (6; 50) consists of: e) primaryparts (21, 24; 51, 54) on the input shaft (2), and on the second hollowshaft (14) and secondary parts (22, 23; 52, 53) on the power take-offshaft (17) and on the first hollow shaft (12), f) a first shift sleeve(25; 55) for the rotationally fixed connection of the input shaft (2) tothe first hollow shaft (12) in off-road travel, and g) a second shiftsleeve (26; 56) for the rotationally fixed connection of the input shaft(2) to the power take-off shaft (17) in road travel and for connectingthe second hollow shaft (14) to the power take-off shaft (17) inoff-road travel.
 2. The power-split transmission as claimed in claim 1,wherein the clutch unit (6) is arranged on that side of the reductionunit (5) which faces the input shaft (2) and the second hollow shaft(14) is arranged within the first hollow shaft (12).
 3. The power-splittransmission as claimed in claim 1, wherein the power take-off shaft(17) can be connected fixedly in terms of rotation to a driving wheel(28) of the offset drive (7) via a cut-in clutch (27).
 4. Thepower-split transmission as claimed in claim 2, wherein the powertake-off shaft (17) is drive-connected to a central differential (8)which is designed as a planetary transmission and which has two axledrive shafts (31, 32), in each case one or other of which canselectively be connected fixedly in terms of rotation to a driving wheel(28) of the offset drive (7) via a cut-in clutch (33).
 5. Thepower-split transmission as claimed in claim 4, wherein the centraldifferential (8) consists of: a) a differential ring gear (34) connectedfixedly in terms of rotation to the power take-off shaft (17), b) a sunwheel (35) connected fixedly in terms of rotation to a second axle driveshaft (32), c) a planet carrier (36) connected fixedly in terms ofrotation to the first axle drive shaft (31) and having first and secondplanet wheels (37, 38), in each case the first planet wheels (37)meshing with the sun wheel (35), the second planet wheels (18) with thedifferential ring gear (34) and the first and second planet wheels (37,38) with one another.
 6. The power-split transmission as claimed inclaim 5, wherein the ring gear (13) and the differential ring gear (34)and/or the intermediate gearwheels (15, 16) and the planet wheels (37,38) are identical parts.
 7. The power-split transmission as claimed inclaim 5, wherein the cut-in clutch (33) comprises: a) first couplingparts (41; 61) connected fixedly in terms of rotation to the first axledrive shaft (31), b) second coupling parts (42; 62) connected fixedly interms of rotation to the second axle drive shaft (32), c) third couplingparts (43; 63) connected fixedly in terms of rotation to the drivingwheel (28) of the offset drive (7), d) a third clutch sleeve (44; 64)which, in two-wheel drive, connects the first (31) and the second (32)axle drive shafts to one another fixedly in terms of rotation, infour-wheel drive connects the second axle drive shaft (32) and theoffset drive (37) to one another fixedly in terms of rotation and, infour-wheel drive with differential lock, connects the first axle driveshaft (31) and the offset drive (7) to one another fixedly in terms ofrotation.
 8. The power-split transmission as claimed in claim 4, whereinthe reduction unit (5) and the central differential (8) are arrangeddirectly adjacently, being followed in the direction of the first outputshaft (3) first by the offset drive (7) and then by the cut-in clutch(33).
 9. The power-split transmission as claimed in claim 1, withsynchronized clutch units, wherein the second shift sleeve (56) isconnected fixedly in terms of rotation, but axially displaceably, to thepower take-off shaft (17).
 10. The power-split transmission as claimedin claim 9, wherein the first shift sleeve (55) and the second shiftsleeve (56) are jointly displaceable in the axial direction, but withaxial play, so that, during the shift back into off-road travel, firstthe first shift sleeve (55) is synchronized with the first hollow shaft(12) and then the second shift sleeve (56) is synchronized with thesecond hollow shaft (14).
 11. The power-split transmission as claimed inclaim 7, with synchronizing clutch units, wherein the third shift sleeve(64) has first coupling parts (62) which are connected fixedly in termsof rotation, but axially displaceably, to the second axle drive shaft(32).
 12. The power-split transmission as claimed in claim 11, whereinthe first coupling parts (62) are displaceable in the axial directionwith respect to the third shift sleeve (64).